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Soil Boring Report — former Chevron Station 99-3232, Stockton CA July 27 1999 Environmental (C57 #683865) under SJCPHS permit dated April 8, 1999. Soil borings using hollow-stem augers were drilled by Bay Area Exploration Inc. (C57 #522125) under SJCPHS permit no. 017173 . Copies of the drilling permits are included in Appendix C. One soil boring (BH- 1 ) was advanced by Geoprobe technology on April 26, 1999. This boring was advanced to 45 .0 feet bgs where refusal was encountered. Four soil borings (BH- IA through BH-4) were drilled on May 5 and 6, 1999 using hollow-stem augers. To complete on-site delineation of residual petroleum hydrocarbons, soil boring BH-5 was drilled on May 28, 1999. These borings were drilled to depths between 60.5 and 70.5 feet bgs using a truck-mounted drill rig equipped with 84nch-diameter hollow-stem augers.. A GR geologist observed the drilling activities, collected soil samples at five-foot intervals for possible chemical analysis, described the encountered soil and prepared a log of each boring. Each boring was backfilled to ground surface with neat cement placed using a tremie pipe and pump. Boring logs are included in Appendix B . Locations of the borings are shown on Figure 2. RESULTS OF THE SUBSURFACE INVESTIGATION Soil encountered during this investigation consisted predominantly of a silty, sandy unit extending from the surface to around 52 to 54 feet bgs, followed by a 7 to 10 foot thick sand unit overlying another silty sandy unit at the base of the borings. In borings BH-2, BH-3 , and BH-5 , the upper silty sandy unit is divided into two parts, separated by a 3 to 4-foot thick sand lens around 15 feet bgs that pinches out westward. In borings BH- 1 and BH-4, sand is encountered to depths between approximately 17 and 27 feet bgs where it is underlain by silt. The sand unit encountered between 52 and 60 feet bgs appears continuous across the site, and consists of greater that 90% very fine to coarse sand with trace silt and clay. Sand grains are mainly quartz with trace lithic fragments. The silty sandy unit below the sand unit consists of interfingered silty sand and sandy silt beds with some clay content varying throughout the unit. Groundwater was encountered between 35 to 45 feet bgs during drilling. These findings are consistent with those found in borings MW- 1 , MW-2, and MW-3 . CHEMICAL ANALYTICAL RESULTS A total of 34 soil samples from the well borings and one composite soil sample from the stockpiled drill cuttings were submitted under chain-of-custody for chemical analysis. Analyses were performed by Sequoia Analytical of Sacramento, California (FLAP # 1624). Copies of the laboratory reports and chain-of-custody forms are included in Appendix D. Soil chemical analytical data are summarized in Tables 1 and 2. Chemical Analytical Procedures All soil samples were analyzed for Total Petroleum Hydrocarbons as gasoline (TPHg) by EPA Modified Method 8015, benzene, toluene, ethylbenzene and total xylenes (BTEX) and Methyl Tertiary-Butyl Ether (MTBE) by EPA Method 8020, and oxygenates by EPA Method 8260 . 346463 .04-2 3